Study On The Interaction Of Puerariae Radix Flavonoids And The Selenium Complex With DNA

The study of the interaction between bioactive small molecules and DNA has become one of the most active research area in biomedicine.A thorough elucidation of the interaction between bioactive small molecules and DNA not only will help to understand the physiological processes and metabolic mechanisms of cells,but also provide important guidance for designing of more efficient drug candidates,providing a strong basis to develop the targeted DNA drugs for the effective control of different diseases.In this paper,Puerariae Radix,a natural product known as "Asian ginseng",was used to study the interaction of Puerariae Radix flavonoids and the selenium complex with different DNA,including single-stranded DNA,double-stranded DNA,quadruplex DNA and circular DNA,to reveal their interaction mechanism from different perspectives,and explore their interaction effects on tumor cells.The specific research contents of this paper were as follows:(1)The interaction between pueraria flavonoids and DNA was evaluated by computational molecular docking,and their affinity was predicted.Since flavonoids had aromatic skeletons in common,the CDOCKER module with high accuracy of docking aromatic molecules was used to study the binding of six flavonoids with double-stranded DNA(ds DNA).According to the predicted score of binding energy,the affinity sequence of six flavonoids to ds DNA was as follows: quercetin >formononetin > daidzein > puerarin > 4’-methoxy puerarin > puerarin 6"-O-xyloside.In addition,the affinity of flavonoids to HIV DNA and G-quadruplex was further studied.The results showed that quercetin,with good DNA affinity,could be considered as a potential lead compound,providing a theoretical basis for subsequent studies.(2)The interaction between pueraria flavonoids and DNA was verified bymulti-spectral analyses,and the theoretical results of molecular simulation docking were confirmed.Several spectroscopic methods were discussed to study the binding affinity of pueraria flavonoids with two different double-stranded DNAs,i.e.synthetic double-stranded DNA(1BNA)and natural calf thymus DNA(CT-DNA).The results showed that the DNA binding affinity of six flavonoids followed the order: quercetin > formononetin > daidzein > puerarin > 4′-methoxy puerarin >puerarin 6″-O-xyloside.The experimental results were consistent with the trend predicted by molecular docking,indicating that quercetin had the best affinity with DNA.Moreover,this study was carried out to derive biophysical characteristics of the interactions,which provide an important basis for confirming the structure-activity correlation.These studies provided a new way for the screening and development of natural active lead compounds with better targeting.(3)The interaction between pueraria flavonoids and DNA was further studied with DNA amplified by rolling circle.Meanwhile,the bioactivity screening platform based on DNA rolling circle amplification was established,which could be directly observed by a simple visual gel imaging system.The results showed that quercetin,with the strongest affinity with DNA,had a significant inhibitory effect on DNA amplification,while the other five flavonoids had no obvious DNA inhibitory activity.(4)Quercetin,which has the strongest affinity with DNA of different types and functions,was used as a lead compound to form a new flavonoid-selenium complex combined with selenium ion,and the interaction between quercetin-selenium complex and DNA was studied.Firstly,the structure of the flavonoid-selenium complex was designed and optimized by molecular docking.With the assistance of multi-spectral analyses and the DNA inhibition screening platform,the aimed flavonoid-selenium complex was synthesized and its molecular structure was analyzed.Finally,the interaction between the novel flavonoid-selenium complex and DNA of different structures and functions was investigated.The results indicated thatvarious excellent biological activities of quercetin and selenium were respectively combined in the flavonoid complex.This study provided a new strategy for the design and development of anti-tumor drugs targeting DNA.(5)According to the high affinity between quercetin or its selenium complex and DNA of different structures and functions,the effect of their interaction with DNA on tumor cells was studied.The uptake of quercetin and its selenium complex in cells were firstly explored,then their effects on the cell cycle and apoptosis of tumor cells were investigated,and biological activities in the cytoplasm or even nucleus through the cell membrane were exhibited.The results showed that the bioactivity of the quercetin-selenium complex was significantly higher than that of the ligand quercetin,especially the cytotoxicity to the MCF-7 human breast cancer cell line increased by 8 times.These ideas gave a new perspective on the design and development of anti-tumor drugs targeting DNA for prevention or combination therapy.